Which is your diagnosis?

EDITORIAL

Which is your diagnosis?

Felipe Ferreira de Souza^I; Marcelo Bordalo Rodrigues^II

^IMD, Resident 3rd year in Radiology at Clinics Hospital Institute of Radiology (InRad), Faculty of Medicine, Universidade de São Paulo

^IIMD, Director of the Radiology Service at Clinics Hospital Institute of Orthopedics, Faculty of Medicine, Universidade de São Paulo

^{Mailing address}

Female patient, 58 years old, complaining of non-painful tumoration at the posterior portion of the thigh, for four months.

Description of the images

Figure 1: Left thigh plain x-ray demonstrating increase in soft tissues, with no evidence of associated bone lesions.

Figure 2: Computed tomography (CT). Bulky, solid, heterogeneous lesion predominantly hyper attenuating with areas of fat attenuation (–20 UH). There are non-contrast-enhanced areas compatible with liquefaction.

Figure 3: T1-weighted axial magnetic resonance imaging (MRI) showing a quite heterogeneous lesion with a solid component; presenting noticeable hyper signal areas. At the T2-weighted axial image with fat saturation, the signal suppression of lesions with T1 hyper signal is evidenced, indicating the presence of fat tissue.

Figure 4: T1-wieghted coronal MRI with multiloculated lesion presenting septations with low signal and hyper signal areas. At T2-weighted coronal view with fat saturation, the presence of septations with hypo signal and signal suppression of the areas with fat component are noticeable. In the post-contrast with fat saturation series there is a heterogeneous impregnation of the lesion with non-contrast-enhanced areas.

Figure 5: MRI. At the T1-weighted image, a large lesion on the posterior portion of the thigh and the cleavage plane with the femur are observed. At the T1 sagittal post-gadolinium image, heterogeneous enhancement of the mass is noted. There are non-enhanced areas suggesting necrosis.

Diagnosis: Pleomorphic liposarcoma.

COMMENTS

Liposarcomas are the most common soft tissues tumors, accounting for approximately 20% of all sarcomas in adults⁽¹⁾.

The pleomorphic variant is the rarest one, accounting for about 5% of all liposarcomas⁽²⁾. It occurs predominantly in patients >50 years old and is very rare in the childhood. These tumors typically appear in the deepest tissues of limbs proximal portions, predominantly in the thigh (30% a 40% of cases).

Radiographically, liposarcomas present as slightly heterogeneous and well defined masses likely to calcify.

It is not possible to differentiate among sarcomas types through x-ray.

At CT it is possible to observe alterations due to the presence of fat tissue (hypo attenuating areas). Intravenous injection of contrast media may show relevant enhancement areas corresponding to hyper vascular regions.

The MRI has become the technique of choice for identifying and classifying soft tissues tumors. The pleomorphic liposarcomas MRI appearance varies considerably, depending both on macro and microscopic alterations⁽³⁾.

At MRI, it is possible to note the fat content of the tumor, although this does not occur in 100% of cases. When fat is present (high signal in T1 and low signal in T2), typically it is irregular, associated with thick septa and solid components, the latest being the most relevant tumoral component in the great majority of times, with isosignal/hyposignal in relation to the muscle at T1-weighted images and hyper signal at T2-weighted images.

Gadolinium saturation is observed, occurring in an intense and heterogeneous way which reflects the vascular nature of these lesions. Besides, the gadolinium is of help in the differentiation of tumoral necrosis areas.

According to the World Health Organization classification, the liposarcomas can be divided into five well differentiated categories (lipoma-like, sclerosant and inflammatory), myxoid, round cells, pleomorphic (only 5% of cases) and differentiated.

Macroscopically, pleomorphic liposarcomas are firm, multinodular and lobulated lesions, with a white-yellowish surface⁽⁴⁾. In some cases, myxoid and/or necrosis areas are observed.

Microscopically, they present a high degree of pleomorphism, including bizarre giant cells, and the diagnosis is based on the identification of pleomorphic, multivacuolated lipoblasts with bizarre and hyperchromatic nucleus, which in some cases may be very scarce, with identification of just a few pleomorphic lipoblasts⁽⁴⁾. Therefore, the greatest part of the neoplasm is compounded of tumoral pleomorphic, spindle cells and cluster of multinucleated giant cells⁽⁵⁾. Frequently, we also may find extra and intracellular eosinophilic globules representing lysosomal structures. Rarely, a great local inflammatory reaction occurs.

The pleomorphic liposarcomas treatment is based on a comprehensive resection of the lesion. Some studies preconize post-surgical radiotherapy, but there is no consensus on such conduct yet.

Among the pleomorphic liposarcomas differential diagnosis one should include other liposarcomas, the high degree and pleomorphic variants of myxofibrosarcomas, the leiomyosarcomas, the rhabdomyosarcomas, the carcinomas and the melanoma.

As regards the prognosis, pleomorphic liposarcomas are aggressive tumors, presenting a survival rate of 29%–57%^(6,7). Among the factors related to a worse prognosis, we may highlight central localization, tumors > 10 cm, high mitotic rate, presence of necrosis, epithelioid morphology. Metastases occur principally to lungs and liver.

REFERENCES

1. Guillou L, Coindre JM, Bonichon F, et al. Comparative study of the National Cancer Institute and French Federation of Cancer Centers Sarcoma Group grading systems in a population of 410 adult patients with soft tissue sarcoma. J Clin Oncol 1997;15:350–362.

2. Azumi N, Curtis J, Kempson RL, Hendrickson MR. Atypical and malignant neoplasms showing lipomatous differentiation: a study of 111 cases. Am J Surg Pathol 1987;11:161–183.

3. Arkun R, Memis A, Akalin T, Ustun EE, Sabah D, Kandiloglu G. Liposarcoma of soft tissue: MRI findings with pathologic correlation. Skeletal Radiol 1997;26:167–172.

4. Fletcher CDM, Unni KK, Mertens F, editors. World Health Organization Classification of Tumours: Pathology and Genetics of Soft Tissue and Bone. Lyon: IARC Press, 2002.

5. Enzinger FM, Weiss SW. Soft tissue tumours. 3rd ed. St Louis: Mosby, 1995.

6. Hornick JL, Bosenberg MW, Mentzel T, McMenamin ME, Oliveira AM, Fletcher CD. Pleomorphic liposarcoma: clinicopathologic analysis of 57 cases. Am J Surg Pathol 2004;28:1257–1267.

7. Gebhard S, Coindre JM, Michels JJ, et al. Pleomorphic liposarcoma: clinicopathologic, immunohistochemical, and follow-up analysis of 63 cases: a study from the French Federation of Cancer Centers Sarcoma Group. Am J Surg Pathol 2002;26:601–616.

Publication Dates

• Publication in this collection
  25 May 2006
• Date of issue
  Apr 2006